An Endfire/Backfire Reconfigurable Leaky Wave Antenna by Radiating Different Space Harmonics

A novel technique is proposed for the design of an endfire/backfire reconfigurable leaky wave antenna (LWA) by radiating different space harmonics. The antenna with a period of about a quarter wavelength can produce a unidirectional endfire beam through the radiation from the fundamental space harmonic. If the period is doubled, the antenna produces a unidirectional backfire beam through the main radiation from the ${n} = -1$ space harmonic, with negligible radiation from the fundamental space harmonic and with other space harmonics far away from the radiation region. Using p-i-n diodes to tune the period in the antenna, the desired fundamental/ ${n} = -1$ radiating space harmonic can be obtained, and then, the endfire/backfire radiation can be reconfigured. Besides, to reduce the performance differences between the forward and backward radiation and to enhance the gain, the antenna is designed with a symmetric structure and fed at the center, in which the left-half and right-half apertures are operated in backfire and endfire states for forward radiation and vice versa. A prototype of the antenna is designed at 5.2 GHz, which reaches peak gains of 9.94 and 9.89 dBi with bandwidths of 23.7% and 25.6% in the forward and backward states, respectively.